1. Field of the Invention
The present invention relates to a charged particle beam system for the inspection and analysis of a sample, a sample processing method, and a semiconductor inspection system.
2. Background Art
A typical example of the cause of defects that lead to a decrease in the yield of semiconductor devices, such as microprocessors and memories, is the attaching of particles to the sample (such as a wafer). The attachment of particles, such as an electrically conductive particle attaching between patterns to cause a short-circuit, or an insulative particle attaching to a connector portion of a wiring pattern to cause conduction failure, causes defective devices. Thus, it is necessary to identify the source of such particles and prevent their development. One method of identifying a source of particles is to analyze the elements of the particle to infer its cause. The method, ultimate analysis, can be performed by means of an energy dispersive X-ray (EDX) system, whereby a substance is irradiated with an electron beam to cause the substance to emit characteristic X-ray whose energy spectrum allows the identification of its elements.
Currently, for the detection of particles, optical inspection systems having a high throughput are generally employed. An optical inspection system includes a stage on which a sample is mounted. While the stage is moved, the sample surface is imaged with an optical microscope, or irradiated with laser light so as to detect scattered light on the sample surface, in order to provide a sample image, based on which adjacent cells or dice are compared to detect a defect portion.
The sample in which a defect has been detected by the optical inspection system is often handed over to a scanning electron microscope for analysis of the defect at higher resolution. The review SEM is a scanning electron microscope for defect analysis which is capable of auto defect review or auto defect classification; some review SEM's are equipped with the EDX functions. However, not every defect detected by the optical inspection system can be confirmed with the scanning electron microscope. For example, if a particle exists in a silicon oxide film or a transparent resist film, the scanning electron microscope can only obtain the information about the film surface and not the information about the particle inside the film, even if the particle inside the film has been established by the optical microscope. The inability of the SEM image to confirm the particle means that the location to be irradiated with an electron beam for ultimate analysis cannot be determined, so that the EDX functions cannot be taken advantage of.
Thus, when a particle inside a film is analyzed, an FIB (focused ion beam) processing system is used. Specifically, the film is machined until the particle or the like appears at the surface, and then the thus exposed particle is observed with an SEM or subjected to EDX analysis.
Currently, the ion source of an FIB generally employs a liquid metal ion source (LMIS), such as Ga (gallium). In the case of an FIB processing system using an LMIS, there is the problem of the LMIS becoming attached to the FIB irradiated surface of the sample, resulting in the development of contamination. Thus, samples that have been processed with an FIB have been unable to be returned to the production line and had to be discarded. In EDX analysis too, the LMIS creates a main cause of preventing an accurate ultimate analysis of a particle.
Another method to expose a particle in the film does not employ an FIB processing system but involves exposure and etching of the sample to process the film on the sample surface so as to expose the particle in the film (see Patent Document 1).
Patent Document 1: JP Patent Publication (Kokai) No. 11-340291 A (1999)